1. . Field of the Invention
The present invention relates to a backpack-type working machine such as a power blower, a power sprayer, or a brush cutter that comprises a mechanical unit (fan, reduction gear or the like) and a power unit (engine) on a shouldering frame and operates the power unit and the like by using a control device on a swingable arm.
2. Description of the Related Art
FIGS. 2A and 2B show a power blower for cleaning as an example of a backpack-type working machine. While these figures relate to the present invention, the configuration or usages described herein for the mechanical unit and power unit are identical to that of the prior art. As shown in FIGS. 2A and 2B, an exemplary power unit, an engine 3, and an exemplary mechanical unit, a fan 5, are mounted on a shouldering frame 2 with a shouldering belt 2a. A flexible tube 6 is connected to an outlet of the fan 5 and has a discharge port (not shown) of cleaning air at an end thereof. An operator trying to clean trash or fallen leaves in a wide place, holding a discharge duct (not shown) at the end of the tube 6 and directing it to a spot to be cleaned, moves around in order to gather the trash or the like. A throttle lever 40 is provided at an end of a controller 10 mounted on a side of the shouldering frame 2. The operator controls the speed (the number of revolutions per unit of time) of the engine 5 by using the lever 40.
FIGS. 6A and 6B show a configuration in which a controller is attached to the conventional backpack-type working machine. This working machine is described in Japanese Utility Model Application Publication No. 7-6780. A holder 20xe2x80x2 is fixed to a side (left-hand side of the operator) of the shouldering frame 2xe2x80x2. A base of an arm 30xe2x80x2 of the controller 10xe2x80x2 is connected to the holder 20xe2x80x2 by means of a bolt 36xe2x80x2 and a nut 37xe2x80x2 through a spring 38xe2x80x2. The bolt 36xe2x80x2 is a pivot around which the arm 30xe2x80x2 swings. The spring 38xe2x80x2 sets a connecting force between the base of the arm 30xe2x80x2 and the holder 20xe2x80x2 to allow the arm 30xe2x80x2 to swing while being braked moderately. The operator shoulders the working machine, swings the arm 30xe2x80x2 of the controller 10xe2x80x2 directed upward as shown in FIG. 6A toward a horizontal point where the arm 30xe2x80x2 is easy-to-handle as shown in FIG. 6B, and then operates the throttle lever 40xe2x80x2 at the end thereof.
In the conventional working machine, the holder 20xe2x80x2 fixed to the shouldering frame 2xe2x80x2 or the like and the base of the arm 30xe2x80x2 which swings as described above are connected such that their contact surfaces 23xe2x80x2, 33xe2x80x2 are in close contact with each other as shown in FIG. 6A. For this reason, the arm 30xe2x80x2 swings on the surface 23xe2x80x2 of the holder 20xe2x80x2, that is, around the bolt 36xe2x80x2 orthogonal to the surface 23xe2x80x2.
In the illustrated example of FIGS. 6A and 6B, the arm 30xe2x80x2 extends in a direction not orthogonal to the bolt 36xe2x80x2 around which the arm 30xe2x80x2 swings. Therefore, the end portion (throttle lever 40xe2x80x2) of the arm 30xe2x80x2 moves as shown by a virtual line xe2x80x9cyxe2x80x9d of FIGS. 6A and 6B along with the swing of the arm 30xe2x80x2, and the arm 30xe2x80x2 swings such that it turns on a conical plane.
In the conventional backpack-type working machine in which the contact surface 23xe2x80x2 of the fixed holder 20xe2x80x2 and the contact surface 33xe2x80x2 of the base of the swingable arm 30xe2x80x2 closely contact each other as shown in FIG. 6A, there is a tendency that the arm 30xe2x80x2 highly vibrates and a shocking external force is unintentionally applied on the holder 20xe2x80x2 or the arm 30xe2x80x2. The reason for the high vibration of the arm 30xe2x80x2 is that vibration of an engine or the like tends to be transmitted to the arm 30xe2x80x2 through contact portions of the holder 20xe2x80x2 and the base of the arm 30xe2x80x2 because their surfaces are in close contact with each other. When the arm 30xe2x80x2 vibrates highly, an arm of the operator holding the arm 30xe2x80x2 is exhausted. The reason why the arm 30xe2x80x2 or the like is subject to the shocking external force is that the surface of the holder 20xe2x80x2 and the surface of the base of the arm 30xe2x80x2 are in close contact with each other and therefore they are under strong restraint, so that when the arm 30xe2x80x2 is bumped into something and a force in a direction different from a normal swing direction (on a plane orthogonal to the bolt 36xe2x80x2) is unintentionally applied on the arm 30xe2x80x2, it concentrates on the contact portions (contact surfaces 23xe2x80x2, 33xe2x80x2). When the force is great, a part of the holder 20xe2x80x2 or the base of the arm 30xe2x80x2 might be deformed or broken off.
When the arm 30xe2x80x2 extends in the direction not orthogonal to the bolt 36xe2x80x2 around which the arm 30xe2x80x2 swings as shown in FIG. 6A, the arm of the operator holding the arm 30xe2x80x2 so as to operate the throttle lever 40xe2x80x2 is unnaturally twisted when the operator swings the arm 30xe2x80x2. When the end (throttle lever 40xe2x80x2) of the arm 30xe2x80x2 moves along the virtual line xe2x80x9cyxe2x80x9d, the operator""s arm holding the arm 30xe2x80x2 in the vicinity of the end moves on the conical plane along with the arm 30xe2x80x2, so that the operator feels discomfort in operation.
The present invention has been developed for the purpose of obviating the aforesaid problem of the conventional working machine, and an object of the present invention is to provide a backpack-type working machine including a controller arm which is capable of absorbing a shocking external force satisfactorily, which makes an operator feel less exhausted, and is easy to handle.
In one aspect of a backpack-type working machine according to the present invention, the backpack-type working machine comprises a power unit (engine or motor) mounted on a shouldering frame, and a swingable arm having a control device such as a throttle lever or access dial, which is attached to a side of the backpack-type working machine(a right-hand or left-hand side of the operator), and is characterized in that (1) a base of the arm is connected to a holder provided integrally with a body of the machine, such as the shouldering frame, the engine, or the like, for supporting the arm at a swing center of the arm by using a pivot, such as a bolt or a pin around which the arm swings through an elastic body such as a spring or a rubber, and (2) the base of the arm and the holder are connected with each other such that the arm and the holder abut with each other at a part of an inclined surface formed between the arm and the holder, to allow the arm to move on a plane orthogonal to a direction, that is, a plane including a center line of the pivot in which the arm swings.
With this configuration, since the swingable arm is on the side of the machine and is provided with the control device, the operator shouldering the working machine can swing the arm to a point where the arm is easy to handle and control the power unit by using the control device. According to the configuration (1) mentioned above, the arm can swing around the pivot while being braked moderately by a force of the elastic body with the base connected to the holder.
Further, according to the configuration (2) mentioned above, in a case where an external force is applied on the arm in the direction different from the normal swing direction, no excess stress is generated at the arm or the holder portion. This is because when the external force including a force component in the direction orthogonal to the normal swing direction (on the plane including the center line of the pivot) is applied on the arm, the arm moves in the direction of the external force. More specifically, since the holder and the base of the arm are connected at a part of the inclined surface in contact with each other according to configuration (2), the arm can swing on the plane including the center line of the pivot unless the other portions of the inclined surfaces make contact with each other. As a result, if the arm. is bumped into something and thereby the external force is unintentionally applied on the arm, no strong reaction force is generated at the arm or the holder.
In addition, in the backpack-type working machine, no high vibration is transmitted to the arm during operation of the power unit. With the configuration (2), since only small areas of the holder and base are in contact with each other, the vibration on the holder which is close to the power unit is likely to be shut off at the contact portions and is less likely to be transmitted to the arm, which makes the operator feel less exhausted.
In another aspect of the backpack-type working machine according to the present invention, convex and concave portions for engagement (recesses formed on one of the holder and the arm and convex portions formed on the other) that maintain angles of the arm at positions where an end of the arm is directed upward and forward (when the operator shoulders the machine) are formed at opposite surfaces of the holder and the base of the arm in a direction of a center line of a pivot between the holder and the base of the arm.
The convex and concave portions for engagement so formed, make it possible that the arm can swing as described above and is maintained with the end thereof directed upward or forward. The upward position is suitable for storage and the forward position is suitable for the operator to hold the arm and operate the arm, that is, when the arm is directed upward, the arm is stored so that it does not protrude from the machine, while when the arm is directed forward, the operator holds the arm and operates the working tool in comfort. Because the arm can be maintained at such positions, this backpack-type working machine is preferable in that the arm can be positioned appropriately depending on whether or not the machine is in use. It should be noted that the arm can swing to another position from the position where it is maintained.
In a further aspect of the backpack-type working machine according to the present invention, the holder portion is formed of; fiber-reinforced- plastic (FRP), for example, GFRP using glass fiber as reinforcement, while the arm is formed of plastic that is not fiber-reinforced, for example, nylon, polyethylene, or polypropylene.
Since the plastic is light weight and is not rusty in contrast with metal, the plastic having some degree of mechanical strength can be a material of constituents of the backpack-type working machine. While the arm or the holder may be formed of the plastic, it is required that the holder have high strength and high hardness, because the holder is a part for supporting the swingable arm via the pivot and is subject to the external force applied on the arm, and its supporting force acts on a small area. In addition, if the holder portion is low in rigidity, the operation of the arm gives the operator undesirable feeling. On the other hand, it is desired that the arm be relatively flexible so as not to generate excess stress at the base of the arm and the holder, when the external force is applied on the arm, and the vibration is not transmitted to the operator""s hand during operation.
To meet this demand, as mentioned above, the holder portion is formed of the fiber-reinforced plastic (FRP) that has high strength and hardness, while the arm is formed of the plastic not fiber-reinforced that has low strength and low hardness, but high elongation to absorb displacement and vibration. With this configuration, the holder withstands a long-term use and as the arm is reasonably flexible, the high stress due to the external force is prevented from generating at the base of the arm and the holder when the arm is bumped into something and exhaustion of the operator due to the vibration is reduced.
In a still further aspect of the backpack-type working machine according to the present invention, the pivot is placed horizontally on a side of the shouldering frame such that the pivot is on a left-hand- or right-hand side of the operator and an outer end thereof is directed obliquely rearward, when the operator shoulders the working machine, and the arm extends in a direction orthogonal to the center line of the pivot.
With this configuration, since the arm swings according to the movement of the operator""s forearm when the operator bends the operator""s elbow, the operator can operate the arm naturally.
More specifically, since the arm extends in the direction orthogonal to the pivot around which the arm swings, the arm swings on a single plane rather than the conical plane already described with reference to FIG. 6. For this reason, the arm of the operator holding the arm in the vicinity of the control device can adapt itself to the movement of the swinging arm. Further, since the pivot is inclined such that the outer end thereof is directed obliquely rearward, the end of the arm extends to the side from the front of the operator when the arm is swung and the end thereof is directed forward. When the arm is thus directed forward and the end thereof thus extends to the side, the operator""s arm is extended naturally and the arm is easy to hold. Therefore, the operator can hold the end of the arm in comfort and continue to work without feeling exhausted for a long time. Moreover, since the pivot is directed horizontally, the arm can be positioned vertically when the arm extending orthogonal to the pivot is swung upward, and therefore the working machine is compactly stored.
This object, as well as other objects, features and advantages of the invention will become more apparent to those skilled in the art from the following description taken with reference to the accompanying drawings.